Great question! I'm looking forward to reading responses, as I too, wonder which implement is best.

My only experience is with a regular-length riding crop. I was surprised to find that it makes a nice, loud snapping sound but hurts very little. So I guess it's great for those who love the "idea" of getting cropped. Of course, if you hit hard enough, it can be painful, but I would say it's safe to use liberally on tougher parts of the body (butt, thighs, calves, etc.) and safe to use carefully on softer parts. It's more noise and less pain than even a mild spanking or slapping.

If you can, look for a store like Toys in Babeland (Seattle and NYC) or Early to Bed (Chicago) where you can go in to a nice boutique and actually try the stuff out. Sometimes even the chain stores like Lovers Package or Lovers Lane have the stuff out. Bring your partner and try stuff out. Then go home and try it out some more.